1. Field of the Invention
The present invention relates to melt cast explosives, propellants and pyrotechnics and especially to the formation of stable emulsions of nitrated energetic materials such as trinitrotoluene and desensitizers such as wax or polymeric materials and the melt casting of the emulsions.
2. Description of the Prior Art
Trinitrotoluene is the most widely used explosive and pyrotechnic in the military and the industrial market. Other much more energetic and dangerous explosive materials are sometimes used separately and often are dispersed into molten trinitrotoluene before casting, or admixed as solid particles. A problem with such materials has been the shock and/or thermal sensitivity of the materials which sometimes resulted in premature detonations.
Many years ago, it was discovered that natural wax such as beeswax, carnauba wax, Ozokerite and Montan wax could be used to desensitize these explosives. In the period of 1940-1960, it was found that petroleum wax and many other chemicals having similar wax-like physical properties such as stearic acid and its sodium, calcium and barium salts, cetyl alcohol, low molecular weight polyethylene wax, polyethoxyethanediol and its monoesters such as stearate, could also be used to desensitize these explosives. Because of its low cost and good desensitizing characteristics, fully refined paraffin wax and microcrystalline wax from petroleum became the most widely used desensitizers. The most widely used U.S. government specification for such wax is MIL-W-20553D, Wax, Desensitizing, originally issued in 1962.
The process used most widely to formulate the explosives and pyrotechnics is the trinitrotoluene melt cast system. Trinitrotoluene is melted by heating in a steam jacketed stirred kettle to 87.degree.-95.degree. C., about 1 to 10 weight percent of the desensitizing wax is added and stirred vigorously to emulsify the wax into the molten trinitrotoluene. The melt is then cast into the munitions case and cooled to solidify. The emulsifiers for incorporating the wax into the molten trinitrotoluene are dispersed in the wax purchased for this application as specified by MIL-C-18164A(OS), 1968 Composition D-2. The emulsifiers are 14 weight percent nitrocellulose, 2 weight percent lecithin in 84 weight percent MIL-W-20553D wax. Solid particles of other explosives such as cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), cyclotetramethylene tetranitramine (HMX) and 3-nitro-1,2,4-triazol-5-one (NTO) and aluminum powder are very often dispersed into the molten trinitrotoluene to the extent of about 40 to 70 weight percent of the total mix. Composition D-2 containing the wax and emulsifiers, varies from about 1 to 10 weight percent of the total mix. The emulsifiers serve a dual function, acting as a dispersant to uniformly disperse the solid particles, at the same time emulsifying the molten wax into the molten trinitrotoluene. These emulsion systems are anhydrous, and this invention does not relate to aqueous emulsion systems of explosives.
In another process, a larger amount of the desensitizing wax is used so it acts as the liquid vehicle for the solid particles at a temperature above the melting point of the wax but below the trinitrotoluene melting point. This is cast loaded into the munition case.
In another process, explosive particles, particularly RDX and HMX, are coated with desensitizing wax and press cast.
Recently the military has had a large continuing program to develop more insensitive high explosives. Serious problems have been encountered with the nitrocellulose emulsifier in the composition D-2 desensitizer used in the trinitrotoluene melt cast system. The nitrocellulose has settled to the bottom of some composition D-2 containers so that the nitrocellulose content of the charge to the mix kettles has been erratically variable. The nitrocellulose also coats out as a hard, difficult to remove layer on the sidewalls of the kettle. Emulsification of the wax is deficient, resulting in defective castings. An undesirable gassing problem has proven to be caused by reaction of the trinitrotoluene with the nitrocellulose.
Much effort has been directed towards finding a new better emulsifier system, without success.
Petroleum oil, SAE 10 engine oil, MIL-0-2104, and Gulf Crown E oil have been found to be successful desensitizer replacements for desensitizing wax in Composition B and with RDX.
An object of the present invention is to provide novel trinitrotoluene/desensitizer melt emulsion castings which are superior to the heretofore available emulsion castings containing nitrocellulose which resulted in defective cast explosives due to nitrocellulose separating and reacting with trinitrotoluene to form gas. These emulsions and castings may also contain other dispersed particles of high explosives such as cyclo-1,3,5-trimethylene-2,4,6-trinitroamine, cyclotetramethylene tetramitramine and/or 3-nitro-1,2,4-triazol-5-one (NTO) and/or aluminum powder. These explosive materials may be used in military or industrial explosive or pyrotechnic applications. Another object of the present invention is to provide emulsifying and dispersing agents consisting of suitable amines, amides, organic salts or polyfunctional organic and derivative compounds, having usefulness in the easier, more reliable preparation of trinitrotoluene/desensitizer melt emulsion castings of better quality, including safety. Another object of this invention is to provide the above in the case where the desensitizer is a wax or wax-like material or a petroleum oil. These and other objects and benefits of the present invention will become more readily apparent from a reading of the following detailed description.
It has now been found that trinitrotoluene/desensitizer melt emulsion castings can be prepared without the use of any deleterious nitrocellulose emulsifier, which was always required before, by using certain emulsifiers as provided in accordance with the present invention.